The cylindrical or parallelepipedal cans, which are used for storing bulk products, have at their upper wall an opening occupying a large area. The closing of said cans is achieved by applying a lid onto said opening, in order to avoid loss of the content stored inside the can, regardless of the position of said cans. Such lids have a reinforced peripheral edge, in order to prevent said lids from suffering damages during the opening of the can, which may avoid said opening. This reinforcement is calculated to give more strength to the lid.
In a known construction, the peripheral edge of the lid is seated against a corresponding closing seat, which is defined at the edge of the central opening and which is projected onto an upper wall portion of said can, said portion being disposed at a lower plane in relation to the plane of the reinforced peripheral edge of the can, thereby allowing said peripheral edge to act as a supporting point for the application of a lever used to remove said lid during the opening of the can.
In the Brazilian Utility Model Application MU 7301199, of the same applicant, a new construction is described for the upper wall of the cans provided with discharge openings, in which the lid is seated against a corresponding closing seat, defined at an annular step provided at the internal peripheral edge of the upper wall, said step being positioned at the lower portion of a median annular region of the upper wall that is located radially between said step and the external edge of said upper wall.
In these constructions, the internal edge of the upper wall has, at the region where the closing seat is defined, a tubular wall portion, which is downwardly projected towards the inside of the can, and which terminates in a free end in contact with the content of the can and with a lid wall portion, radially projecting beyond said end, in order to cause the locking of the lid to the can when the lid is seated onto the closing seat of the discharge opening of said can.
An inconvenience of said tubular wall constructions refers to the possibility of the stored product being contaminated by the contact thereof with the radial internal face of the free end of the tubular wall, which face is not varnished as the can inside, thus allowing the occurrence of oxidation and the above cited contamination of the product. This oxidizing contact, in the case of liquid products, results from a film of this liquid that remains between the adjacent contact surfaces of the tubular wall of the central opening and the annular wall of the lid. The film between said surfaces results from the absence of restriction to the access of the liquid to the can opening region.
Another inconvenience of these constructions refers to the fragile lid-central opening closing, in which the locking is obtained only by fitting an annular portion of the lid tubular wall, which has a diameter slightly larger than that of the central opening free end and which acts against the latter when said lid is removed. To permit the closing and opening movements of the can, said annular portion is elastically deformed from a locking position to a retracted position, said deformation being easily obtained due to the fragile locking, thus allowing the involuntary opening of the can.
A still further inconvenience of these constructions refers to the possibility of the user being hurt when handling the can, due to the fact that the tubular wall of the central opening terminates in a sharp edge.